1. Field of the Invention
The present invention relates to a method of and an apparatus for ripping a plate material, and to a plate material. The plate material is a material used to manufacture, for example, a head suspension of a disk drive installed in an information processing apparatus such as a personal computer.
2. Description of Related Art
A disk drive installed in an information processing apparatus contains a rotating magnetic disk or magneto-optical disk and a head suspension that is provided with a head or an element to write and read data to and from the disk. In the disk drive, the head suspension is supported with an arm of a carriage that is driven by an actuator.
The head suspension includes a base plate, a load beam, and the like that are made from plate materials. In practice, a plurality of head suspensions are chained together at predetermined pitches in a frame and are separated from the frame into individual head suspensions as disclosed in Japanese Unexamined Patent Application Publication No. 2000-57723.
FIGS. 7A, 7B, and 7C are sectional views illustrating a method of separating a chained head suspension from a frame according to a related art, in which FIG. 7A partly illustrates the chained head suspension, FIG. 7B illustrates the chained head suspension set on a shearing apparatus, and FIG. 7C illustrates the head suspension separated from the frame.
In FIG. 7A, the chained head suspension 101A includes a base plate, a stiffener 103 welded to the base plate, and a resilient part 107 spot-welded to the stiffener 103. The resilient part 107 is integral with the frame 105.
The chained head suspension 101A is separated from the frame 105 into an individual head suspension 101. For this, an upper pad 110 of the shearing apparatus 109 is lowered to hold the resilient part 107 and stiffener 103 between the upper pad 110 and a lower die 111 as illustrated in FIG. 7B. Then, a punch 113 is lowered to shear a part between the frame 105 and the resilient part 107, thereby producing the individual head suspension 101.
To prevent burrs from occurring during shearing with the punch 113 and die 111, a clearance CL between the punch 113 and the die 111 is set to be very small. For example, the clearance CL is set to several microns and a surface roughness of each of the punch 113 and die 111 facing the clearance CL is set to have a maximum height Ry in submicron.
Narrowing the clearance CL between the punch 113 and the die 111, however, increases the cost of the shearing apparatus 109.
To solve this problem, there is a ripping technique that allows a clearance between the punch and the die to be roughly set.
FIGS. 8A, 8B, and 8C illustrate a ripping apparatus according to a related art, in which FIGS. 8A and 8B are sectional views and FIG. 8C a plan view of the ripping apparatus.
In FIGS. 8A and 8B, the ripping apparatus 115 has an upper pad 117, a lower die 119, a punch 121, and a lower pad 123. The lower pad 123 is supported with, for example, a spring so that the lower pad 123 may descend when the punch 121 is lowered.
In FIG. 8C, a resilient part 107 of a chained head suspension 101A is connected to a frame 105 through an easily breaking part 125.
The chained head suspension 101A is fed into the ripping apparatus 115 so that the stiffener 103 and resilient part 107 of the chained head suspension 101A are positioned between the punch 121 and the lower pad 123.
The punch 121 and upper pad 117 are lowered, and on one side of the easily breaking part 125, the frame 105 is held between the upper pad 117 and the die 119.
The punch 121 is lowered relative to the lower pad 123, to clamp the stiffener 103 and resilient part 107 between them on the other side of the easily breaking part 125 and break or rip the easily breaking part 125.
This separates the chained head suspension 101A from the frame 105 into an individual head suspension 101.
According to the related art of FIGS. 8A to 8C, the easily breaking part 125 is sometimes not aligned with an edge of the punch 121, to apply oblique tension to the easily breaking part 125. Such oblique tension causes a burr as illustrated in FIG. 8B when the easily breaking part 125 is ripped.
In the case of the head suspensions 101A chained together through the frame 105, heat during welding and the like may vary pitches among the chained head suspensions 101A, to cause burrs as illustrated in FIG. 8B during the ripping process.